About the 200mm fan : it is clearly noisier than the Noctua. Second problem : it can't work at very low speed (too heavy, too high hysteresis). Third problem, the place : on the top of the case, it is in direct way to my ears. The best places for fans are inside the case (as i did), on the back, or behind the front door.

I replace the 200mm fan with a simple peace of metal (not so easy : it was stuck. If you want to remove it, be careful !).

About the possibility of flipping the PSU fan as an intake fan : The Power Supply is the second hot spot of my computer (after the CPU). I did several tests on the subject (see my pic on page 1 with the four cases). My conclusions on the PSU were :
- no intake fan for PSU (never),
- and separate air flow between PSU and CPU (not in serial).

Hi, part of the reason you can't measure the very slow fan speeds is the Noctua fans themselves. I've used 120mm and 80mm Noctua's and they don't seam to put out any speed signal below about 6V. It seams to me some fans can read at very low speed and others can't
Also often have to configure SpeedFan to get the low rpm readings.
SpeedFan -> Configure -> Advanced -> Winbond xxxx (or whatever the monitoring chip on your board is) -> FanX divisor. Choice of powers of 2 for setting, I find it defaults to 4-8 and need at least 32 for low fan speeds, tick the "remember it" box too.
I've just been experimenting with a Xilence 1500rpm 80mm fan and can read it's speed down to 285rpm at 30%, 25% and it stops altogether.
Regards, Seb

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